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 A144521 Tetrahedral numbers k*(k+1)*(k+2)/6 such that exactly one of k, k+1, and k+2 is prime. 1
 0, 20, 56, 84, 165, 220, 364, 455, 680, 816, 1140, 1330, 1771, 2024, 2300, 3654, 4060, 4960, 5456, 7770, 8436, 9139, 10660, 11480, 13244, 14190, 16215, 17296, 18424, 23426, 24804, 26235, 32509, 34220, 37820, 39711, 47905, 50116, 52394, 57155 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS EXAMPLE k=0: Of the three numbers (0,1,2), exactly one is prime, so 0*1*2/6 = 0 is in the sequence. k=1: Of the three numbers (1,2,3), exactly two are prime, so 1*2*3/6 = 1 is not in the sequence. k=4: Of the three numbers (4,5,6), exactly one is prime, so 4*5*6/6 = 20 is in the sequence. MAPLE isPr := proc(n) if isprime(n) then 1; else 0; end if; end proc: for n from 0 to 300 do if isPr(n)+isPr(n+1)+isPr(n+2) = 1 then printf("%d, ", n*(n+1)*(n+2)/6 ) ; end if; end do: # R. J. Mathar, May 01 2010 CROSSREFS Cf. A000040, A000392, A141468, A152622, A152916. Sequence in context: A108108 A316935 A123456 * A044122 A044503 A109806 Adjacent sequences:  A144518 A144519 A144520 * A144522 A144523 A144524 KEYWORD nonn AUTHOR Juri-Stepan Gerasimov, Dec 15 2008 EXTENSIONS Corrected (455, 14190, 17296 inserted, 16560 removed etc.) by R. J. Mathar, May 01 2010 Name and Example section clarified by Jon E. Schoenfield, Aug 06 2017 STATUS approved

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Last modified October 30 16:01 EDT 2020. Contains 338081 sequences. (Running on oeis4.)